arXiv subjects

S. Shenawy

Publications and source records attributed to S. Shenawy.

2 recordsLinked to original sources

arXiv2016

On symmetries of generalized Robertson-Walker Space-times and applications

The purpose of the present article is to study and characterize sev- eral types of symmetries of generalized Robertson-Walker space-times. Con- formal vector fields, curvature and Ricci collineations are studied. Many im- plications for existence of these symmetries on generalied Robertson-Walker spacetimes are obtained. Finally, Ricci solitons on generalized Robertson- Walker space-times admitting conformal vector fields are investigated.

math.DG↗

arXiv2013

On the boundary of closed convex sets in $E^{n}$

In this article a class of closed convex sets in the Euclidean $n$-space which are the convex hull of their profiles is described. Thus a generalization of Krein-Milman theorem\cite{Lay:1982} to a class of closed non-compact convex sets is obtained. Sufficient and necessary conditions for convexity, affinity and starshapedness of a closed set and its boundary have been derived in terms of their boundary points.

math.MG↗